It has long been known to fabricate containers by blow-moulding, wherein a preform is inflated into the form of a container by the injection of a pressurized gas therein. The preform generally comprises a hollow, tubular body fabricated from a thermoplastic resin, having a cavity, a plain closed end, and a finished open end generally provided with threads or other means for engaging a closure device.
During the moulding process, the preform is disposed within the cavity of a mould which defines the form of a container, and then a pressurized gas is injected into the preform to induce it to expand into the form of a container. Preferably, a stretching rod is also advanced into this preform during the injection of the pressurized gas so as to induce it to stretch longitudinally during the blow-moulding process, yielding a greater degree of control over the longitudinal deformation of the preform during injection.
Recently, it has become known to perform the blow-moulding process with an incompressible working fluid rather than with a gas. The use of an incompressible fluid as the working fluid yields a greater degree of control over the expansion of the container. Furthermore, the incompressible fluid may be retained in the container after fabrication is completed; where the incompressible fluid is a liquid product, this enables the fabrication and filling of containers in a single step.
However, in the case of pressurized gas blow molding technology such systems are disadvantageous in that, as with the traditional pressurized-gas blow moulding systems, one may not fabricate multiple containers at once without furnishing a mould for each container to be fabricated with each cycle of the apparatus. These moulds are generally furnished as two or three segments, each segment defining a portion of the container surface and machined from a single block of aluminium or high-strength steel. Such moulds are complex and thus often expensive and time-consuming to fabricate, particularly in the quantities that are required for the operation of a high-volume container fabricating installation such as a beverage bottling line.
The prior art is insufficient to resolve this issue. For instance, the U.S. Pat. No. 2,013,382 (“GARWOOD”) discloses two embodiments of a method for fabricating a container having two chambers, by two different methods. In the first embodiment, two separate molten-glass parisons are disposed within the same mould. During the glassblowing process the two containers merge with each other, forming a single container with two cavities and two openings. In the second embodiment, a single gob of molten glass is provided with two cavities, forming a two-chambered parison which is subsequently blown into a single container with two cavities and two openings.
However, GARWOOD does not fabricate a plurality of containers, but merely a single double-chambered container; the two chambers cannot be separated without breaking, cutting, or otherwise permanently modifying the container. Nor does GARWOOD resolve the expense required in furnishing mould assemblies for each container being fabricated. Moreover, the use of such moulds also lengthens the container fabrication cycle, in that it requires time to open and close the mould, and to insert the parison(s) and extract the finished container. This additional time lengthens the duration of a container fabrication cycle and therefore comprises a limitation on the output of a container fabrication system.
U.S. Pat. No. 6,355,204 also describes a method for manufacturing a single double-chambered container.
A further constrain to be mentioned in the case of use of pressurized gas blow molding technology is that the control and coordination of pressurized gas injection for simultaneous injections has not been yet optimised.
Finally, such systems are disadvantageous in that any additional packaging elements, such as labels or bindings, must be provided in a separate step with separate equipment. This adds further complication and expense to the operation of a container production installation.
It is therefore an object of the invention to provide a method for fabricating a plurality of containers which resolves at least some of the above issues.